Interoception is the sensing of signals from internal organs, and it is essential for the maintenance of body homeostasis. Dysregulation of interoceptive control has been linked to behavioral problems such as anxiety and panic disorder, but the underlying cause was unknown. Pharmacological approaches that reduce heart rate and vagal-nerve stimulation have a well-described inhibitory effect on anxiety. In a recent issue of Nature, Hsueh et al. show that the increase in heart rate can trigger an anxiety-like behavior in mice.
The researchers developed a noninvasive optogenetic tool that enables external control of heart rate without mouse sedation or opening the mouse chests to expose the heart to light. More specifically, they used genetic manipulations to generate mice that produce a photosensitive bacterial opsin only in cardiomyocytes. Red light illumination activated the cardiomyocyte opsin, leading to ventricular tachycardia. These genetically modified mice wore a special vest with a micro-LED that delivered red light with deep tissue penetration, sufficient to activate the cardiomyocyte opsin and increase the heart rate from 600 to 900 beats per min. This experimental setup enabled the mouse behavior to be monitored, as the animals could roam free and be subjected to several behavioral tests.
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